1. Field of the Invention
This invention is related to a rim structure for a bicycle wheel. The invention is also related to a bicycle wheel having such a rim, as well as to a wheel having such a rim equipped with a tire.
The invention especially relates to a rim of the butt or hook type that is designed for a so-called xe2x80x9ctubelessxe2x80x9d assembly, or in other words, without an air tube.
2. Description of Background and Relevant Information
In a known manner, a wheel has a rim and a hub connected to the rim via two sets of spokes. The rim generally includes two bridges connected to one another by lateral flanks that extend beyond the upper bridge via rim flanges so as to form an annular channel where the tire can become housed. At their upper portions, the rim flanges have a butt-like or a hooked portion whose function is to retain the tire after inflation. Normally, the bridges of the rim are bored with openings that are used for the passage or retention of the spoke nipples.
Tubeless assemblies for tires are known. Such an assembly is advantageous because it eliminates the cost, mounting and weight of an air tube. In addition, such an assembly makes the wheel equipped with the tire less prone to punctures due to pinching or perforation. A thorn, for example, that passes through the tire remains, in effect, embedded in its housing, so that hardly any air, or just a negligible amount of air, is lost.
In order to obtain a tubeless assembly of the tire, it has been known to block all the openings of the spokes by a sealed rim base. The patent application EP 615 865 discloses such a technique. However, it is difficult to seal all of the spoke openings. In order to remedy this, the above-cited application also proposes that the lips of the tire cover the edges of the rim base, so as to form a closed volume along with it. This requires a special type of tire, whose assembly is a delicate operation.
In order to overcome the sealing problem of the rim, the patent application DE 42 06 311 also proposes obtaining a rim whose upper bridge is not bored. The spokes are thus anchored in the openings of the lower bridge. The fact that the upper bridge is smooth, i.e., it has no holes except for the valve opening, resolves sealing problems in this area. In addition, such a rim is compatible with conventional tires. However, this solution gives rise to a sealing problem between the sides of the tire and the rim. The problem becomes apparent when the tire is inflated, especially if the inflation is done with a low output device, such as a manual pump, for example. In fact, when the tire is mounted on the rim, the tire is positioned along only a small portion the width of the upper bridge. Under these conditions, the quantity of air blown into the tire by a pump escapes at various points between the sides and the upper bridge, thereby achieving neither inflation, nor any seal.
This problem also becomes apparent while riding the cycle, if the tire is not adequately pressed against the sides of the rim. In case of a lateral impact, for example caused by a stone, the air can escape if the tire becomes removed from the rim, especially if its pressure is low. Indeed, in such a case, the sides of the tire are no longer pushed up against the rim flanges by the air tube.
An object of the invention is to propose an improved rim that is provided for a tubeless assembly of the tire.
Another object of the invention is to propose a rim whose contour improves tire inflation conditions.
Yet another object is to propose a rim whose contour improves the retention of the tire when it is inflated.
Other objects and advantages of the invention will become apparent from the following description.
The rim for a bicycle wheel according to the invention has an annular channel along its periphery which is provided to receive the tire, such channel being demarcated by an upper bridge devoid of openings with the exception of the valve opening, and two lateral flanges, such flanges having butts designed to grip the tire. The upper bridge has a narrow and recessed rim well demarcated by a base and two lateral walls, the rim well being bordered by two bead seats, at least partially inclined, so that the external diameter of the rim in the area of the bead seats decreases from the well towards the flanges.
The bicycle wheel according to the invention has a rim such as defined previously.